The present invention relates in general to improving the conditioning of well fluids, and in particular to an improved apparatus and method for conditioning well fluids that are pumped through artificial lift assemblies.
A typical well production fluid lift system utilizes an artificial lift assembly having a centrifugal pump mounted to the lower end of a string of production tubing in the well casing. The electrical motor for rotating the pump is usually located below the pump. The well fluid circulates around the pump assembly and is drawn into an intake port, which is usually located on the lower end of the pump. The well fluid is then pumped out through the string of tubing to the surface.
Well fluid commonly contains a number of impurities including sediment, production debris, such as rubber particles and other man-made trash, and scale, which is a naturally occurring substance. Sediment and production debris reduce efficiency and can cause damage as they pass through the system. If left untreated, scale causes plugging and wear in the pump assembly, as well as harmful deposition on the exterior of the pump assembly. External scale deposition causes elevated operating temperatures which can lead to reduced operational life. Thus, due to the presence of impurities in well fluid, it is desirable for the fluid being drawn into the pump to be at least somewhat xe2x80x9cconditionedxe2x80x9d to reduce the harmful effects of the impurities.
In the prior art, a number of methods and systems have been devised to improve the life and efficiency of production fluid lift systems in these harsh environments. Sand separators have been secured to the bottom of the pump assembly for separating sediment from the well fluid before reaching the pump. Nucleation devices for removing scale have also been mounted to the pump assembly. The weight of these devices is supported by the pump assembly. Due to the structural limitations of the pump assembly, the number and weight of the tools that can be deployed to further treat the well fluid are restricted.
In FIG. 1A of U.S. Pat. No. 4,749,034, a cylindrical jacket 27 is mounted to the lower end of the pump assembly 15 near its intake 19. The jacket limits the source of the well fluid entering the pump to an axial passage 39 (FIG. 1C). The jacket acts as an intake manifold for injecting additional cutting fluid (port 47) into the pump from the surface in order to reduce the viscosity of the well fluid. The entire weight of the jacket assembly is physically supported at flange 29 on pump 15 (FIG. 1A).
U.S. Pat. No. 4,537,257 describes a device for lifting well fluids that isolates the tubing/casing annulus from the produced fluids. As shown in FIG. 1 a shield 12 surrounds the pump assembly 11 and is sealed at its upper and lower ends with end caps 13, 14, respectively. Although the shield 12 is mounted directly to the string of production tubing 40 extending from the surface, additional tubing 20 is required below the shield. The extra tubing 20 must be sealed off against the wellhead casing 10 below the pump with a separate annular sealing device 30 (FIG. 2A). Each of the embodiments disclosed (FIGS. 2A-2C) require this additional seal support below tubing 20. Tubing 20 allows completely unconditioned well fluid to enter and circulate around the lift system. An improved system and method for conditioning well fluids that are pumped through artificial lift assemblies is needed.
An artificial lift assembly is suspended from a string of conduit such as production tubing in a well inside a well casing. An encapsulation module is independently suspended from the conduit and encases the artificial lift assembly with a jacket. A series of well fluid conditioning tools are mounted to the lower end of the jacket. These tools may include a tubular screen, a desander located behind the screen, a string of disposal tubing extending below the desander, and a nucleation device located above the desander. Not all three clarifying tools are required in each well. The entire weight of this fluid conditioning equipment is completely supported by the jacket and the conduit.
The encapsulation module is completely sealed so that the well bore fluid is limited to entering the module and pump through the screen. The screen removes larger contaminants from the fluid such as rubber and trash. After the fluid passes through the screen, it enters the desander, if employed, where solid matter such as sediment is removed from the fluid and eliminated through the disposal tubing. Finally, the fluid enters the nucleation device, if employed where its scale is decomposed. After these clarifying phases, the fluid enters the pump assembly and is pumped to the surface.
Accordingly, it is an object of the present invention to provide improved well fluid conditioning.
It is an additional object of the present invention to provide an improved apparatus and method for conditioning well fluids that are pumped through artificial lift assemblies.
The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the preferred embodiment of the present invention, taken in conjunction with the appended claims and the accompanying drawings.